Gas Chromatography (GC). The separation of enantiomers by GC on CSPs was extensively reviewed by Schurig (12), with discussion of the method development, applications, and ancillary techniques of chiral separations using GC. CSPs with amino acid derivatives, terpene-derived metal coordination compounds, and modified cyclodextrins were included. Schurig also comprehensively reviewed the practice and theory of enantioselective complexation GC on optically active metal(II) bis[3-perfluoroacyl)-(1R)-camphorate] selectors (13). Applications extend to chiral analysis in asymmetric synthesis, enzymic reactions, pheromone, and flavor chemistry. The elucidation of thermodynamic parameters of enantioselectivity and the investigation of the enantiomerization of configurationally labile enantiomers was also discussed.Thin-Layer Chromatography (TLC). The development of stationary phases for TLC in the last 10 years was compiled by Gocan ( 14), and included chiral separation and recent advances in chiral stationary phases. The CSPs discussed included nonpolar bonded stationary phases impregnated with transitional metal ions, cellulose, modified cellulose, chitin, chitosan, and their derivatives. Cyclodextrin and macrocyclic antibiotics were reported to have very good results for enantioseparation by TLC, with molecular imprinting polymers also finding use as CSPs in TLC.Capillary Electrochromatography. The applications of CEC were reviewed by Remcho et al. (15). Chiral separations with cyclodextrins and their derivatives, biomolecules, molecularly imprinted polymers, "brush"-type phases, ion exchangers, antibiotics, polysaccharide derivatives, and other CSPs were included in this review. A summary of recent progress in open-tubular CEC for chiral and achiral separations included stationary-phase preparation ( 16), with the major developments, potential applications, technical difficulties, and advantages of each wall coating discussed.Multiple Technique Reviews. The use of cyclodextrins in chiral chromatography was compiled by Juvancz and Szejtli (17). The role of cyclodextrins in methods using capillary columns such as GC, supercritical fluid chromatography (SFC), and CE was detailed, as well as their use in other forms of chromatography such as HPLC and TLC. The mechanism of chiral recognition using cyclodextrins was also discussed. Williams and Wainer (18) reviewed the role of chiral chromatography in therapeutic drug monitoring and in clinical and forensic toxicology. Enantioselective GC and HPLC were used as tools to unravel complex phenomena associated with drug transport and metabolism.

A protocol has been developed that allows protein identifications using available DNA-based or protein sequences from a reference strain of a bacterial species to be extended to bacterial strains for which no prior DNA-based or protein sequence information exists. The protocol is predicated on careful isolation of a specific sub-cellular group of proteins. In this study, ribosomal proteins were chosen due to their high relative abundance and similarity in copy number per cell. After isolation of ribosomal proteins, MALDI-MS is used to acquire accurate protein molecular weights. An iterative comparison of reference protein molecular weights and identities is made to the resulting data, allowing for the straightforward identification of ribosomal proteins from any non-reference strains. This approach can reveal differences between proteins at the amino acid or post-translational level. The protocol was developed, validated and applied to ribosomal proteins from three strains of the extreme thermophile Thermus thermophilus. This approach revealed that nearly 60% of the ribosomal proteins from all three strains are identical. The extension of protein identification to additional bacterial strains can be useful in phylogenetic studies as well as in biomarker identification.

Ribosomal protein S12 contains a highly conserved aspartic acid residue that is posttranslationally ␤-methylthiolated. Using mass spectrometry, we have determined the modification states of several S12 mutants of Thermus thermophilus and conclude that ␤-methylthiolation is not a determinant of the streptomycin phenotype.Streptomycin and streptomycin-resistant mutants have played a seminal role in the elucidation of the decoding process of protein synthesis (reviewed in reference 19). Genetic and biochemical analyses of ribosomes from streptomycin-resistant mutants implicated ribosomal protein S12 as the determinant of the various streptomycin phenotypes, including resistance, dependence, and pseudodependence (reviewed in references 11 and 17). Such mutations have been localized in the three-dimensional structure of the Thermus thermophilus 30S ribosomal subunit to reside within two highly conserved loops centered around residues P90 and K42 (Escherichia coli numbering used throughout) ( Fig. 1) (7).It has only recently been discovered by use of mass spectrometry that E. coli ribosomal protein S12 is posttranslationally modified via a ␤-methylthiolation at position D88 ( Fig. 2A), near the streptomycin binding site and in the midst of residues altered in streptomycin-resistant mutants (14). This modification has also been found to occur in the phototrophic bacterium Rhodopseudomonas palustris (22), and we have identified it for the extremely thermophilic bacterium T. thermophilus (24). Posttranscriptional modifications of rRNA residues have been shown to affect resistance to various antibiotic classes (reviewed in reference 8). For example, ksgA mutants are resistant to kasugamycin due to the loss of N6-dimethylation of two conserved adenosines in 16S rRNA (13), while methylation of rRNA in the peptidyltransferase center (21) or in the decoding region (3) confers resistance to erythromycin and aminoglycosides, respectively (reviewed in references 20 and 26).Interestingly, loss of modification of a ribosomal protein has not yet been shown to affect antibiotic sensitivity. Nevertheless, the proximity of S12 residue D88 to residues altered in streptomycin-resistant mutants raises the possibility that such mutations might confer resistance indirectly by inhibiting ␤-methylthiolation of D88. To address this question, we performed matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) to establish the modification status of ribosomal protein S12 in a series of streptomycinresistant and streptomycin-dependent mutants of T. thermophilus.Loss of ␤-methylthiolation in a subset of S12 mutants. We examined the modification states of several S12 mutants of T. thermophilus IB-21 (ATCC 43815) (16) by MALDI-TOF MS as described previously (23). Wild-type S12 was determined to have a mass of 14,519 Ϯ 6 Da (Table 1), consistent with our previous report (24), indicating loss of the initial methionine and the presence of the ␤-methylthiolation. Considering the proximity to D88, we sought to deter...

Our understanding of the structural organization of ribosome assembly intermediates, in particular those intermediates that result from mis-folding leading to their eventual degradation within the cell, is limited due to the lack of methods available to characterize assembly intermediate structures. Because conventional structural approaches, such as NMR, X-ray crystallography and cryo-EM, are not ideally suited to characterize the structural organization of these flexible and sometimes heterogeneous assembly intermediates, we have set out to develop an approach combining limited proteolysis with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) that might be applicable to ribonucleoprotein complexes as large as the ribosome. This study focuses on the limited proteolysis behavior of appropriately assembled ribosome subunits. Isolated subunits were analyzed using limited proteolysis and MALDI-MS and the results were compared to previous data obtained from 70S ribosomes. Generally, ribosomal proteins were found to be more stable in 70S ribosomes than in their isolated subunits, consistent with a reduction in conformational flexibility upon subunit assembly. This approach demonstrates that limited proteolysis combined with MALDI-MS can reveal structural changes to ribosomes upon subunit assembly or disassembly, and provides the appropriate benchmark data from 30S, 50S and 70S proteins to enable studies of ribosome assembly intermediates.